The production of phenol from cyclohexylbenzene is an emerging technology, interesting in that it co-produces cyclohexanone, rather than acetone. Cyclohexylbenzene may be produced, for example, by direct alkylation of benzene with cyclohexene, or as disclosed in U.S. Pat. No. 6,037,513, by contacting benzene with hydrogen in the presence of a catalyst. The cyclohexylbenzene may then be oxidized to the corresponding hydroperoxide and the hydroperoxide cleaved to phenol and cyclohexanone using a catalyst.
The production of phenol and cyclohexanone from cyclohexylbenzene also produces various contaminants that are difficult to separate from the desired products. However, the nature of those contaminants and the separations thereof are significantly different from those in the conventional Hock process for the production of phenol and acetone, and/or the conventional cyclohexanone production from cyclohexane or phenol. For example, hydroalkylation of benzene produces significant amounts of, among others, cyclohexane and lesser amounts of methylcyclopentane, cyclohexene, phenylcyclohexene, and phenylcyclohexyldiene. Similarly, the oxidation of cyclohexylbenzene typically produces peroxide species alien to the Hock process, such as the desired cyclohexyl-1-phenyl-1-hydroperoxide (CHBHP), and undesired byproduct hydroperoxides such as cyclohexyl-1-phenyl-2-hydroperoxide, cyclohexyl-1-phenyl-3-hydroperoxide and cyclohexyl-1-phenyl-4-hydroperoxide. The cleavage of these various hydroperoxides produces a wide variety of contaminant species which are not produced by the chemistry and technology of either the Hock process, the cyclohexane oxidation process, or the phenol hydrogenation process. The yields and energy efficiency in the oxidation, cleavage and separation steps determine the final cost and quality of the phenol and cyclohexanone product.
The contaminants in the phenol product can significantly impact the quality of products made from phenol, such as bis-phenol A, polycarbonates, phenolic resins, and the like.
Cyclohexanone is widely used to make caprolactam, which, in turn, is used for making nylon-6, a widely used polymer material. The purity of caprolactam has significant impact on the quality such as strength of nylon-6 made therefrom. For example, in various industrial processes for making cyclohexanone, methylcyclopentanone may be produced as a contaminant. Even at a very small amount, methylcyclopentanone may lead to the formation of highly undesirable contaminants, particularly methylvalerolactams, which is very difficult to remove from caprolactam. The various isomers of methylvalerolactam, by polymerization with each other and/or with caprolactam, may significantly reduce the quality and performance of the nylon-6 product, even at a low concentration.
As such, there is a strong need of a system for making high purity phenol and cyclohexanone at high yields in the oxidation, cleavage and separation steps, desirably with high energy efficiency.